Food casings based on cellulose have been used for decades for the production of e.g. raw sausages, dry sausages and semi-dry sausages.
In the manufacture of processed sausage products, a meat emulsion is prepared from comminuted meat together with fillers, seasonings etc. A tubular food casing, such as one containing non-edible cellulose, may be loaded onto the stuffing horn of a filling machine and stuffed with meat emulsion. Depending on the type of sausage product, the casing may be twisted, tied or clipped into suitable size, or formed into chubs or sticks, and further processed.
Dry or semi-dry sausages, occasionally referred to as cervelats or summer sausages, are larger sausage products and include such representative examples as air dried pepperoni, soft salami, hard salami and dry salami, and the like. This type of sausage has reduced moisture content, and its preparation usually includes drying as one step of its manufacture. A dry sausage may also be smoked. Cooking may also be performed in some instances in the smoking step. Some sausages may be fermented during their processing.
There are significant variations in the compositions of the meat emulsions used affecting the processing and the final product. Further, the size of the sausage product and consequently the size, e.g. diameter, of the food casing may vary greatly. There are also variations in the ripening and respective drying cycles to reach a final protein to fat ratio and/or moisture to protein ratio. Ripening and drying is characterized by weight loss ranging from approx. 10 to 30%, which is associated with a reduction in volume and mainly radial shrinkage.
Due to the above reasons, it may be challenging to optimize the production of dry or semi-dry and other sausage products. The drying and/or ripening rate is important. The food casing should adhere sufficiently to the sausage or meat emulsion to avoid grease or oil spot formation between the sausage or meat emulsion and the food casing. The adverse phenomenon where grease or oil spots are formed between the sausage or meat emulsion and the food casing is often called greasing out. In addition to being unsightly, greasing out also reduces the rate of ripening and/or drying. Greasing out may also have adverse effects at peeling, because the grease or oil may increase adherence of the meat emulsion to the food casing.
Furthermore, the food casing should adhere to an extent that allows peeling off the casing using different peeling procedures, including e.g. manual or fast speed automatic peeling. Automatic peeling apparatuses and methods have been developed for large scale production of sausage products. For instance, known are apparatuses having mechanisms for inflating the casing with pressurized air, for removing the end caps of the casing, for slitting and removing the casing from the sausage product, and for positioning the sausage products for these operations. Efficient and fast processing of sausage products, e.g. pork and pepperoni sausages, requires the use of higher production temperatures, which may result in significant greasing out. Naturally, productivity in the production of sausage products should be maintained at an acceptable level for economical reasons.
Several methods and chemical agents have been proposed for improving, i.e. increasing or reducing, adhesion of a food casing to proteins, meat emulsions or sausage products, and for allowing suitable release and peeling of the food casing.
However, these approaches may have various limitations and drawbacks. For instance, fluctuation due to variation in the amount of fibre on the inside surface of a cellulose-based food casing depending on the degree of viscose penetration may result in overly high adhesion, particularly for sausage types requiring the combination of high weight loss during ripening and drying and fast or automatic peeling.
The use of chemical agents, for instance internal impregnation or coating of a food casing with an adhesion promoting agent and/or a release agent, may be difficult to optimize. For instance, the agents may be incompatible (e.g. in terms of hydrophilicity) and thus require additional components as emulsifiers; the agents may be costly or not well suitable for use in food applications; or it may be difficult to find a suitable balance between the agents and the desired characteristics of the food casing. Furthermore, the agents may be susceptible to varying conditions due to chemical or mechanical steps during the manufacture of the food casing, or there may be fluctuations in the amount of the agents in the food casing, leading to inconsistencies in the food casings or manufactured batches thereof and their performance during the manufacture of the sausage product.